Hi
I am wondering if someone could please advise on the issue of seismic analysis.
Issue1: If during natural frequency analysis mass participation is such that a huge number of modes to be taken into account in order to capture sufficient amount of mass, then what to do? Should one select a Mode cut off range and use ZPA to complete the mass participations? And for force calculations use acceleration at ZPA to calculate the force? But how to get ZPA acceleration?
Issue 2: For completing an equivalent analysis: I am thinking about carrying out a natural frequenccy (or modal) analysis and then get sufficient modes to obtain a sufficient amount of mass. Do I then need to use SRSS or CQC etc. techniques to combine modes? If so then how to work out the acceleration for the calculations of the forces?!
Thanks.